This invention relates generally to conveyor systems, and more particularly to chain conveyor assemblies used in manufacturing.
To create efficiency in production, conveyors are often used to provide automated transportation of products between workstations. For example, it is common to suspend parts from a conveyor as they are moved through a paint booth and/or assembly workstation. The conveyor permits the parts to be carried at a constant rate, allowing even application of paint. Conveyors can operate for long periods of time, eliminating the need for transportation manpower and the possibility of human error in manual transport.
A common form of these conveyors is the chain conveyor. Chain conveyor assemblies generally include a chain that is driven around a facility by a motor. Hangers or other similar structures can be attached to the chain so that parts can be easily attached and removed. A conventional chain conveyor typically includes a number of male and female links that are interconnected one after another to form the full length of the chain.
A result of the prolonged use of conveyors is deterioration, caused by the friction between interfacing parts. This deterioration can occur in numerous places. For instance, in chain conveyors there is a relatively high amount of friction induced deterioration at the point of interface between the male and female chain links. Over time the material starts to erode, causing the chain to stretch and eventually requiring an expensive rebuild or replacement of the entire chain.
A common attempt to reduce the deterioration of conveyor parts is through the application of lubricants. By lubricating the conveyor, the friction between parts is reduced and the life of the chain is extended. Many lubricating systems are available that can be attached to or near the chain and programmed to pump a lubricant onto the conveyor at regular intervals. Unfortunately, the lubricant application equipment, and lubricants themselves, are expensive and can cause problems by dripping onto floors and products. For example, lubricant drippings and over-spray that fall on a part can interfere with the application of paint and other coatings to the part. Lubricants also entrap and retain dirt and dust that can affect wear and other operational aspects of the conveyor.
Another attempted solution is to case harden the conveyor chain. By hardening the chain, the effects of wear can be significantly reduced. To prevent the wear from being focussed on a single component of the chain, it is typically necessary to harden the entire chain, including the links and the connector pins. The hardening process is rather expensive and, although it extends the life of the chain, wear remains a significant concern even with a hardened chain. In fact, wear remains a significant problem even when hardened chains and lubricants are combined.
In applications outside of the conveyor industry, wear issues are sometimes addressed by applying an extremely hard, carbon film coating to the metal parts that are most heavily affected by deterioration. These coatings are often referred to as diamond-like coatings or xe2x80x9cDLCs.xe2x80x9d DLCs can be applied by a variety of techniques, such as ion-beam deposition, sputtering, chemical vapor deposition and the like. Although DLCs are extremely hard, they are also extremely thin. As a result, DLCs are somewhat fragile and quickly deteriorate in high load applications, such as industrial conveyor applications. Consequently, the use of DLC in the industrial conveyor industry has long been considered impractical and infeasible.
The aforementioned problems are overcome by the present invention wherein a conveyor assembly is provided with a chain in which the interface of adjacent links includes the combination of a DLC and a polymeric bushing. The combination is disposed at locations of relative movement between adjacent links so that relative movement between the links occurs between the coated part and the bushing.
In a preferred embodiment, the chain includes male and female links that are interconnected to each other by connector pins. The connector pins are fixed with respect to the female links. The male links are pivotally mounted about the connector pins to provide the chain with flexibility. The DLC is disposed on the outer surface of the connector pin and the bushing is fixed to the male link in interfacing relationship with the DLC coated pin.
In a more preferred embodiment, each male link includes a recess adapted to receive the bushing. The recess is shaped to not only receive, but also to secure the bushing, preventing its rotational movement with respect to the male link.
In another aspect, the present invention is incorporated into a bearing assembly, such as the ball bearing assembly supporting the conveyor chain. In a preferred embodiment, the bearing assembly includes bearings that are coated with a DLC and a raceway assembly that includes polymeric bushings to contact the bearings. Alternatively, the raceways can be manufactured entirely from a polymeric material, eliminating the need for separate bushings.
The present invention provides a simple and effective assembly that reduces wear and dramatically increases the life of high-wear components. The present invention also eliminates the need for conventional lubricating systems. Unlike the conventional use of lubricants and very hard, smooth surfaces to reduce friction between chain links, the present invention achieves improved results by eliminating conventional lubricants and combining the smooth, very hard DLC surface with a softer polymeric bushing at the interface of adjacent moving parts. Further, when necessary, the chain can be refurbished by the replacement of inexpensive bushings as opposed to replacement of the entire chain. The present invention also provides significant advantages in noise reduction.
These and other objects, advantages, and features of the invention will be readily understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings.